/****************************************************************************/
/* This file is part of FreeFem++.                                          */
/*                                                                          */
/* FreeFem++ is free software: you can redistribute it and/or modify        */
/* it under the terms of the GNU Lesser General Public License as           */
/* published by the Free Software Foundation, either version 3 of           */
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/*                                                                          */
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/* but WITHOUT ANY WARRANTY; without even the implied warranty of           */
/* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the            */
/* GNU Lesser General Public License for more details.                      */
/*                                                                          */
/* You should have received a copy of the GNU Lesser General Public License */
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/****************************************************************************/
// SUMMARY : ...
// LICENSE : LGPLv3
// ORG     : LJLL Universite Pierre et Marie Curie, Paris, FRANCE
// AUTHORS : ...
// E-MAIL  : ...

/*
 * PStreams - POSIX Process I/O for C++
 * Copyright (C) 2001-2013 Jonathan Wakely
 *
 * This file is part of PStreams.
 *
 * PStreams is free software; you can redistribute it and/or modify
 * it under the terms of the GNU Lesser General Public License as published by
 * the Free Software Foundation; either version 3 of the License, or
 * (at your option) any later version.
 *
 * PStreams is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU Lesser General Public License for more details.
 *
 * You should have received a copy of the GNU Lesser General Public License
 * along with this program.  If not, see <http://www.gnu.org/licenses/>.
 */

/**
 * @file pstream.h
 * @brief Declares all PStreams classes.
 * @author Jonathan Wakely
 *
 * Defines classes redi::ipstream, redi::opstream, redi::pstream
 * and redi::rpstream.
 */

#ifndef REDI_PSTREAM_H_SEEN
#define REDI_PSTREAM_H_SEEN

#include <ios>
#include <streambuf>
#include <istream>
#include <ostream>
#include <string>
#include <vector>
#include <algorithm>// for min()
#include <cerrno>	// for errno
#include <cstddef>	// for size_t, NULL
#include <cstdlib>	// for exit()
#include <sys/types.h>	// for pid_t
#include <sys/wait.h>	// for waitpid()
#include <sys/ioctl.h>	// for ioctl() and FIONREAD
#if defined (__sun)
# include <sys/filio.h>	// for FIONREAD on Solaris 2.5
#endif
#include <unistd.h>	// for pipe() fork() exec() and filedes functions
#include <signal.h>	// for kill()
#include <fcntl.h>	// for fcntl()
#if REDI_EVISCERATE_PSTREAMS
# include <stdio.h>	// for FILE, fdopen()
#endif

/// The library version.
#define PSTREAMS_VERSION 0x0080	// 0.8.0

/**
 *  @namespace redi
 *  @brief  All PStreams classes are declared in namespace redi.
 *
 *  Like the standard iostreams, PStreams is a set of class templates,
 *  taking a character type and traits type. As with the standard streams
 *  they are most likely to be used with @c char and the default
 *  traits type, so typedefs for this most common case are provided.
 *
 *  The @c pstream_common class template is not intended to be used directly,
 *  it is used internally to provide the common functionality for the
 *  other stream classes.
 */
namespace redi
{
	/// Common base class providing constants and typenames.
	struct pstreams
	{
		/// Type used to specify how to connect to the process.
		typedef std::ios_base::openmode pmode;

		/// Type used to hold the arguments for a command.
		typedef std::vector<std::string> argv_type;

		/// Type used for file descriptors.
		typedef int fd_type;

		static const pmode pstdin = std::ios_base::out;	///< Write to stdin
		static const pmode pstdout = std::ios_base::in;	///< Read from stdout
		static const pmode pstderr = std::ios_base::app;///< Read from stderr

		protected:
			enum {bufsz = 32};	///< Size of pstreambuf buffers.
			enum {pbsz  = 2};	///< Number of putback characters kept.
	};

	/// Class template for stream buffer.
	template<typename CharT, typename Traits = std::char_traits<CharT> >
	class basic_pstreambuf
		: public std::basic_streambuf<CharT, Traits>
		  , public pstreams
	{
		public:
			// Type definitions for dependent types
			typedef CharT char_type;
			typedef Traits traits_type;
			typedef typename traits_type::int_type int_type;
			typedef typename traits_type::off_type off_type;
			typedef typename traits_type::pos_type pos_type;
			/** @deprecated use pstreams::fd_type instead. */
			typedef fd_type fd_t;

			/// Default constructor.
			basic_pstreambuf ();

			/// Constructor that initialises the buffer with @a command.
			basic_pstreambuf (const std::string &command, pmode mode);

			/// Constructor that initialises the buffer with @a file and @a argv.
			basic_pstreambuf (const std::string &file,
			                  const argv_type &argv,
			                  pmode mode);

			/// Destructor.
			~basic_pstreambuf ();

			/// Initialise the stream buffer with @a command.
			basic_pstreambuf *
			open (const std::string &command, pmode mode);

			/// Initialise the stream buffer with @a file and @a argv.
			basic_pstreambuf *
			open (const std::string &file, const argv_type &argv, pmode mode);

			/// Close the stream buffer and wait for the process to exit.
			basic_pstreambuf *
			close ();

			/// Send a signal to the process.
			basic_pstreambuf *
			kill (int signal = SIGTERM);

			/// Send a signal to the process' process group.
			basic_pstreambuf *
			killpg (int signal = SIGTERM);

			/// Close the pipe connected to the process' stdin.
			void
			peof ();

			/// Change active input source.
			bool
			read_err (bool readerr = true);

			/// Report whether the stream buffer has been initialised.
			bool
			is_open () const;

			/// Report whether the process has exited.
			bool
			exited ();

#if REDI_EVISCERATE_PSTREAMS
			/// Obtain FILE pointers for each of the process' standard streams.
			std::size_t
			    fopen(FILE * &in, FILE *&out, FILE *&err);
#endif

			/// Return the exit status of the process.
			int
			status () const;

			/// Return the error number (errno) for the most recent failed operation.
			int
			error () const;

		protected:
			/// Transfer characters to the pipe when character buffer overflows.
			int_type
			overflow (int_type c);

			/// Transfer characters from the pipe when the character buffer is empty.
			int_type
			underflow ();

			/// Make a character available to be returned by the next extraction.
			int_type
			pbackfail (int_type c = traits_type::eof());

			/// Write any buffered characters to the stream.
			int
			sync ();

			/// Insert multiple characters into the pipe.
			std::streamsize
			xsputn (const char_type *s, std::streamsize n);

			/// Insert a sequence of characters into the pipe.
			std::streamsize
			write (const char_type *s, std::streamsize n);

			/// Extract a sequence of characters from the pipe.
			std::streamsize
			read (char_type *s, std::streamsize n);

			/// Report how many characters can be read from active input without blocking.
			std::streamsize
			showmanyc ();

		protected:
			/// Enumerated type to indicate whether stdout or stderr is to be read.
			enum buf_read_src {rsrc_out = 0, rsrc_err = 1};

			/// Initialise pipes and fork process.
			pid_t
			fork (pmode mode);

			/// Wait for the child process to exit.
			int
			wait (bool nohang = false);

			/// Return the file descriptor for the output pipe.
			fd_type &
			wpipe ();

			/// Return the file descriptor for the active input pipe.
			fd_type &
			rpipe ();

			/// Return the file descriptor for the specified input pipe.
			fd_type &
			rpipe (buf_read_src which);

			void
			create_buffers (pmode mode);

			void
			destroy_buffers (pmode mode);

			/// Writes buffered characters to the process' stdin pipe.
			bool
			empty_buffer ();

			bool
			fill_buffer (bool non_blocking = false);

			/// Return the active input buffer.
			char_type *
			rbuffer ();
			buf_read_src
			    switch_read_buffer(buf_read_src);

		private:
			basic_pstreambuf (const basic_pstreambuf &);
			basic_pstreambuf &operator = (const basic_pstreambuf &);

			void
			init_rbuffers ();

			pid_t ppid_;// pid of process
			fd_type wpipe_;	// pipe used to write to process' stdin
			fd_type rpipe_[2];	// two pipes to read from, stdout and stderr
			char_type *wbuffer_;
			char_type *rbuffer_[2];
			char_type *rbufstate_[3];
			/// Index into rpipe_[] to indicate active source for read operations.
			buf_read_src rsrc_;
			int status_;// hold exit status of child process
			int error_;	// hold errno if fork() or exec() fails
	};

	/// Class template for common base class.
	template<typename CharT, typename Traits = std::char_traits<CharT> >
	class pstream_common
		: virtual public std::basic_ios<CharT, Traits>
		  , virtual public pstreams
	{
		protected:
			typedef basic_pstreambuf<CharT, Traits> streambuf_type;
			typedef pstreams::pmode pmode;
			typedef pstreams::argv_type argv_type;

			/// Default constructor.
			pstream_common ();

			/// Constructor that initialises the stream by starting a process.
			pstream_common (const std::string &command, pmode mode);

			/// Constructor that initialises the stream by starting a process.
			pstream_common (const std::string &file, const argv_type &argv, pmode mode);

			/// Pure virtual destructor.
			virtual
			~pstream_common () = 0;

			/// Start a process.
			void
			do_open (const std::string &command, pmode mode);

			/// Start a process.
			void
			do_open (const std::string &file, const argv_type &argv, pmode mode);

		public:
			/// Close the pipe.
			void
			close ();

			/// Report whether the stream's buffer has been initialised.
			bool
			is_open () const;

			/// Return the command used to initialise the stream.
			const std::string &
			command () const;

			/// Return a pointer to the stream buffer.
			streambuf_type *
			rdbuf () const;

#if REDI_EVISCERATE_PSTREAMS
			/// Obtain FILE pointers for each of the process' standard streams.
			std::size_t
			    fopen(FILE * &in, FILE *&out, FILE *&err);
#endif

		protected:
			std::string command_;	///< The command used to start the process.
			streambuf_type buf_;///< The stream buffer.
	};

	/**
	 * @class basic_ipstream
	 * @brief Class template for Input PStreams.
	 *
	 * Reading from an ipstream reads the command's standard output and/or
	 * standard error (depending on how the ipstream is opened)
	 * and the command's standard input is the same as that of the process
	 * that created the object, unless altered by the command itself.
	 */

	template<typename CharT, typename Traits = std::char_traits<CharT> >
	class basic_ipstream
		: public std::basic_istream<CharT, Traits>
		  , public pstream_common<CharT, Traits>
		  , virtual public pstreams
	{
		typedef std::basic_istream<CharT, Traits> istream_type;
		typedef pstream_common<CharT, Traits> pbase_type;

		using pbase_type::buf_;	// declare name in this scope

		pmode readable (pmode mode) {
			if (!(mode & (pstdout | pstderr))) {
				mode |= pstdout;
			}

			return mode;
		}

		public:
			/// Type used to specify how to connect to the process.
			typedef typename pbase_type::pmode pmode;

			/// Type used to hold the arguments for a command.
			typedef typename pbase_type::argv_type argv_type;

			/// Default constructor, creates an uninitialised stream.
			basic_ipstream ()
				: istream_type(NULL), pbase_type()
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param command  a string containing a shell command.
			 * @param mode     the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			basic_ipstream (const std::string &command, pmode mode = pstdout)
				: istream_type(NULL), pbase_type(command, readable(mode))
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param file  a string containing the pathname of a program to execute.
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_ipstream (const std::string &file,
			                const argv_type &argv,
			                pmode mode = pstdout)
				: istream_type(NULL), pbase_type(file, argv, readable(mode))
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling
			 * @c do_open(argv[0],argv,mode|pstdout)
			 *
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_ipstream (const argv_type &argv, pmode mode = pstdout)
				: istream_type(NULL), pbase_type(argv.at(0), argv, mode | pstdout)
			{}

			/**
			 * @brief Destructor.
			 *
			 * Closes the stream and waits for the child to exit.
			 */
			~basic_ipstream ()
			{}

			/**
			 * @brief Start a process.
			 *
			 * Calls do_open( @a %command , @a mode|pstdout ).
			 *
			 * @param command  a string containing a shell command.
			 * @param mode     the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			void
			open (const std::string &command, pmode mode = pstdout) {
				this->do_open(command, readable(mode));
			}

			/**
			 * @brief Start a process.
			 *
			 * Calls do_open( @a file , @a argv , @a mode|pstdout ).
			 *
			 * @param file  a string containing the pathname of a program to execute.
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			void
			open (const std::string &file,
			      const argv_type &argv,
			      pmode mode = pstdout) {
				this->do_open(file, argv, readable(mode));
			}

			/**
			 * @brief Set streambuf to read from process' @c stdout.
			 * @return  @c *this
			 */
			basic_ipstream &
			out () {
				this->buf_.read_err(false);
				return *this;
			}

			/**
			 * @brief Set streambuf to read from process' @c stderr.
			 * @return  @c *this
			 */
			basic_ipstream &
			err () {
				this->buf_.read_err(true);
				return *this;
			}
	};

	/**
	 * @class basic_opstream
	 * @brief Class template for Output PStreams.
	 *
	 * Writing to an open opstream writes to the standard input of the command;
	 * the command's standard output is the same as that of the process that
	 * created the pstream object, unless altered by the command itself.
	 */

	template<typename CharT, typename Traits = std::char_traits<CharT> >
	class basic_opstream
		: public std::basic_ostream<CharT, Traits>
		  , public pstream_common<CharT, Traits>
		  , virtual public pstreams
	{
		typedef std::basic_ostream<CharT, Traits> ostream_type;
		typedef pstream_common<CharT, Traits> pbase_type;

		using pbase_type::buf_;	// declare name in this scope

		public:
			/// Type used to specify how to connect to the process.
			typedef typename pbase_type::pmode pmode;

			/// Type used to hold the arguments for a command.
			typedef typename pbase_type::argv_type argv_type;

			/// Default constructor, creates an uninitialised stream.
			basic_opstream ()
				: ostream_type(NULL), pbase_type()
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param command  a string containing a shell command.
			 * @param mode     the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			basic_opstream (const std::string &command, pmode mode = pstdin)
				: ostream_type(NULL), pbase_type(command, mode | pstdin)
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param file  a string containing the pathname of a program to execute.
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_opstream (const std::string &file,
			                const argv_type &argv,
			                pmode mode = pstdin)
				: ostream_type(NULL), pbase_type(file, argv, mode | pstdin)
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling
			 * @c do_open(argv[0],argv,mode|pstdin)
			 *
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_opstream (const argv_type &argv, pmode mode = pstdin)
				: ostream_type(NULL), pbase_type(argv.at(0), argv, mode | pstdin)
			{}

			/**
			 * @brief Destructor
			 *
			 * Closes the stream and waits for the child to exit.
			 */
			~basic_opstream () {}

			/**
			 * @brief Start a process.
			 *
			 * Calls do_open( @a %command , @a mode|pstdin ).
			 *
			 * @param command  a string containing a shell command.
			 * @param mode     the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			void
			open (const std::string &command, pmode mode = pstdin) {
				this->do_open(command, mode | pstdin);
			}

			/**
			 * @brief Start a process.
			 *
			 * Calls do_open( @a file , @a argv , @a mode|pstdin ).
			 *
			 * @param file  a string containing the pathname of a program to execute.
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			void
			open (const std::string &file,
			      const argv_type &argv,
			      pmode mode = pstdin) {
				this->do_open(file, argv, mode | pstdin);
			}
	};

	/**
	 * @class basic_pstream
	 * @brief Class template for Bidirectional PStreams.
	 *
	 * Writing to a pstream opened with @c pmode @c pstdin writes to the
	 * standard input of the command.
	 * Reading from a pstream opened with @c pmode @c pstdout and/or @c pstderr
	 * reads the command's standard output and/or standard error.
	 * Any of the process' @c stdin, @c stdout or @c stderr that is not
	 * connected to the pstream (as specified by the @c pmode)
	 * will be the same as the process that created the pstream object,
	 * unless altered by the command itself.
	 */
	template<typename CharT, typename Traits = std::char_traits<CharT> >
	class basic_pstream
		: public std::basic_iostream<CharT, Traits>
		  , public pstream_common<CharT, Traits>
		  , virtual public pstreams
	{
		typedef std::basic_iostream<CharT, Traits> iostream_type;
		typedef pstream_common<CharT, Traits> pbase_type;

		using pbase_type::buf_;	// declare name in this scope

		public:
			/// Type used to specify how to connect to the process.
			typedef typename pbase_type::pmode pmode;

			/// Type used to hold the arguments for a command.
			typedef typename pbase_type::argv_type argv_type;

			/// Default constructor, creates an uninitialised stream.
			basic_pstream ()
				: iostream_type(NULL), pbase_type()
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param command  a string containing a shell command.
			 * @param mode     the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			basic_pstream (const std::string &command, pmode mode = pstdout | pstdin)
				: iostream_type(NULL), pbase_type(command, mode)
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param file  a string containing the pathname of a program to execute.
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_pstream (const std::string &file,
			               const argv_type &argv,
			               pmode mode = pstdout | pstdin)
				: iostream_type(NULL), pbase_type(file, argv, mode)
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling
			 * @c do_open(argv[0],argv,mode)
			 *
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_pstream (const argv_type &argv, pmode mode = pstdout | pstdin)
				: iostream_type(NULL), pbase_type(argv.at(0), argv, mode)
			{}

			/**
			 * @brief Destructor
			 *
			 * Closes the stream and waits for the child to exit.
			 */
			~basic_pstream () {}

			/**
			 * @brief Start a process.
			 *
			 * Calls do_open( @a %command , @a mode ).
			 *
			 * @param command  a string containing a shell command.
			 * @param mode     the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			void
			open (const std::string &command, pmode mode = pstdout | pstdin) {
				this->do_open(command, mode);
			}

			/**
			 * @brief Start a process.
			 *
			 * Calls do_open( @a file , @a argv , @a mode ).
			 *
			 * @param file  a string containing the pathname of a program to execute.
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			void
			open (const std::string &file,
			      const argv_type &argv,
			      pmode mode = pstdout | pstdin) {
				this->do_open(file, argv, mode);
			}

			/**
			 * @brief Set streambuf to read from process' @c stdout.
			 * @return  @c *this
			 */
			basic_pstream &
			out () {
				this->buf_.read_err(false);
				return *this;
			}

			/**
			 * @brief Set streambuf to read from process' @c stderr.
			 * @return  @c *this
			 */
			basic_pstream &
			err () {
				this->buf_.read_err(true);
				return *this;
			}
	};

	/**
	 * @class basic_rpstream
	 * @brief Class template for Restricted PStreams.
	 *
	 * Writing to an rpstream opened with @c pmode @c pstdin writes to the
	 * standard input of the command.
	 * It is not possible to read directly from an rpstream object, to use
	 * an rpstream as in istream you must call either basic_rpstream::out()
	 * or basic_rpstream::err(). This is to prevent accidental reads from
	 * the wrong input source. If the rpstream was not opened with @c pmode
	 * @c pstderr then the class cannot read the process' @c stderr, and
	 * basic_rpstream::err() will return an istream that reads from the
	 * process' @c stdout, and vice versa.
	 * Reading from an rpstream opened with @c pmode @c pstdout and/or
	 * @c pstderr reads the command's standard output and/or standard error.
	 * Any of the process' @c stdin, @c stdout or @c stderr that is not
	 * connected to the pstream (as specified by the @c pmode)
	 * will be the same as the process that created the pstream object,
	 * unless altered by the command itself.
	 */

	template<typename CharT, typename Traits = std::char_traits<CharT> >
	class basic_rpstream
		: public std::basic_ostream<CharT, Traits>
		  , private std::basic_istream<CharT, Traits>
		  , private pstream_common<CharT, Traits>
		  , virtual public pstreams
	{
		typedef std::basic_ostream<CharT, Traits> ostream_type;
		typedef std::basic_istream<CharT, Traits> istream_type;
		typedef pstream_common<CharT, Traits> pbase_type;

		using pbase_type::buf_;	// declare name in this scope

		public:
			/// Type used to specify how to connect to the process.
			typedef typename pbase_type::pmode pmode;

			/// Type used to hold the arguments for a command.
			typedef typename pbase_type::argv_type argv_type;

			/// Default constructor, creates an uninitialised stream.
			basic_rpstream ()
				: ostream_type(NULL), istream_type(NULL), pbase_type()
			{}

			/**
			 * @brief  Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param command a string containing a shell command.
			 * @param mode the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			basic_rpstream (const std::string &command, pmode mode = pstdout | pstdin)
				: ostream_type(NULL), istream_type(NULL), pbase_type(command, mode)
			{}

			/**
			 * @brief  Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling do_open() with the supplied
			 * arguments.
			 *
			 * @param file a string containing the pathname of a program to execute.
			 * @param argv a vector of argument strings passed to the new program.
			 * @param mode the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_rpstream (const std::string &file,
			                const argv_type &argv,
			                pmode mode = pstdout | pstdin)
				: ostream_type(NULL), istream_type(NULL), pbase_type(file, argv, mode)
			{}

			/**
			 * @brief Constructor that initialises the stream by starting a process.
			 *
			 * Initialises the stream buffer by calling
			 * @c do_open(argv[0],argv,mode)
			 *
			 * @param argv  a vector of argument strings passed to the new program.
			 * @param mode  the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			basic_rpstream (const argv_type &argv, pmode mode = pstdout | pstdin)
				: ostream_type(NULL), istream_type(NULL),
				pbase_type(argv.at(0), argv, mode)
			{}

			/// Destructor
			~basic_rpstream () {}

			/**
			 * @brief  Start a process.
			 *
			 * Calls do_open( @a %command , @a mode ).
			 *
			 * @param command a string containing a shell command.
			 * @param mode the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, pmode)
			 */
			void
			open (const std::string &command, pmode mode = pstdout | pstdin) {
				this->do_open(command, mode);
			}

			/**
			 * @brief  Start a process.
			 *
			 * Calls do_open( @a file , @a argv , @a mode ).
			 *
			 * @param file a string containing the pathname of a program to execute.
			 * @param argv a vector of argument strings passed to the new program.
			 * @param mode the I/O mode to use when opening the pipe.
			 * @see   do_open(const std::string&, const argv_type&, pmode)
			 */
			void
			open (const std::string &file,
			      const argv_type &argv,
			      pmode mode = pstdout | pstdin) {
				this->do_open(file, argv, mode);
			}

			/**
			 * @brief  Obtain a reference to the istream that reads
			 *         the process' @c stdout.
			 * @return @c *this
			 */
			istream_type &
			out () {
				this->buf_.read_err(false);
				return *this;
			}

			/**
			 * @brief  Obtain a reference to the istream that reads
			 *         the process' @c stderr.
			 * @return @c *this
			 */
			istream_type &
			err () {
				this->buf_.read_err(true);
				return *this;
			}
	};

	/// Type definition for common template specialisation.
	typedef basic_pstreambuf<char> pstreambuf;
	/// Type definition for common template specialisation.
	typedef basic_ipstream<char> ipstream;
	/// Type definition for common template specialisation.
	typedef basic_opstream<char> opstream;
	/// Type definition for common template specialisation.
	typedef basic_pstream<char> pstream;
	/// Type definition for common template specialisation.
	typedef basic_rpstream<char> rpstream;

	/**
	 * When inserted into an output pstream the manipulator calls
	 * basic_pstreambuf<C,T>::peof() to close the output pipe,
	 * causing the child process to receive the end-of-file indicator
	 * on subsequent reads from its @c stdin stream.
	 *
	 * @brief   Manipulator to close the pipe connected to the process' stdin.
	 * @param   s  An output PStream class.
	 * @return  The stream object the manipulator was invoked on.
	 * @see     basic_pstreambuf<C,T>::peof()
	 * @relates basic_opstream basic_pstream basic_rpstream
	 */
	template<typename C, typename T>
	inline std::basic_ostream<C, T> &
	peof (std::basic_ostream<C, T> &s) {
		typedef basic_pstreambuf<C, T> pstreambuf;
		if (pstreambuf *p = dynamic_cast<pstreambuf *>(s.rdbuf())) {
			p->peof();
		}

		return s;
	}

	/*
	 * member definitions for pstreambuf
	 */

	/**
	 * @class basic_pstreambuf
	 * Provides underlying streambuf functionality for the PStreams classes.
	 */

	/** Creates an uninitialised stream buffer. */
	template<typename C, typename T>
	inline
	basic_pstreambuf<C, T>::basic_pstreambuf ()
		: ppid_(-1)	// initialise to -1 to indicate no process run yet.
		, wpipe_(-1)
		, wbuffer_(NULL)
		, rsrc_(rsrc_out)
		, status_(-1)
		, error_(0) {
		init_rbuffers();
	}

	/**
	 * Initialises the stream buffer by calling open() with the supplied
	 * arguments.
	 *
	 * @param command a string containing a shell command.
	 * @param mode    the I/O mode to use when opening the pipe.
	 * @see   open()
	 */
	template<typename C, typename T>
	inline
	basic_pstreambuf<C, T>::basic_pstreambuf (const std::string &command, pmode mode)
		: ppid_(-1)	// initialise to -1 to indicate no process run yet.
		, wpipe_(-1)
		, wbuffer_(NULL)
		, rsrc_(rsrc_out)
		, status_(-1)
		, error_(0) {
		init_rbuffers();
		open(command, mode);
	}

	/**
	 * Initialises the stream buffer by calling open() with the supplied
	 * arguments.
	 *
	 * @param file  a string containing the name of a program to execute.
	 * @param argv  a vector of argument strings passsed to the new program.
	 * @param mode  the I/O mode to use when opening the pipe.
	 * @see   open()
	 */
	template<typename C, typename T>
	inline
	basic_pstreambuf<C, T>::basic_pstreambuf (const std::string &file,
	                                          const argv_type &argv,
	                                          pmode mode)
		: ppid_(-1)	// initialise to -1 to indicate no process run yet.
		, wpipe_(-1)
		, wbuffer_(NULL)
		, rsrc_(rsrc_out)
		, status_(-1)
		, error_(0) {
		init_rbuffers();
		open(file, argv, mode);
	}

	/**
	 * Closes the stream by calling close().
	 * @see close()
	 */
	template<typename C, typename T>
	inline
	basic_pstreambuf<C, T>::~basic_pstreambuf () {
		close();
	}

	/**
	 * Starts a new process by passing @a command to the shell (/bin/sh)
	 * and opens pipes to the process with the specified @a mode.
	 *
	 * If @a mode contains @c pstdout the initial read source will be
	 * the child process' stdout, otherwise if @a mode  contains @c pstderr
	 * the initial read source will be the child's stderr.
	 *
	 * Will duplicate the actions of  the  shell  in searching for an
	 * executable file if the specified file name does not contain a slash (/)
	 * character.
	 *
	 * @warning
	 * There is no way to tell whether the shell command succeeded, this
	 * function will always succeed unless resource limits (such as
	 * memory usage, or number of processes or open files) are exceeded.
	 * This means is_open() will return true even if @a command cannot
	 * be executed.
	 * Use pstreambuf::open(const std::string&, const argv_type&, pmode)
	 * if you need to know whether the command failed to execute.
	 *
	 * @param   command  a string containing a shell command.
	 * @param   mode     a bitwise OR of one or more of @c out, @c in, @c err.
	 * @return  NULL if the shell could not be started or the
	 *          pipes could not be opened, @c this otherwise.
	 * @see     <b>execl</b>(3)
	 */
	template<typename C, typename T>
	basic_pstreambuf<C, T> *
	basic_pstreambuf<C, T>::open (const std::string &command, pmode mode) {
		const char *shell_path = "/bin/sh";

#if 0
		const std::string argv [] = {"sh", "-c", command};
		return this->open(shell_path, argv_type(argv, argv + 3), mode);
#else
		basic_pstreambuf<C, T> *ret = NULL;

		if (!is_open()) {
			switch (fork(mode)) {
			case 0:
				// this is the new process, exec command
				::execl(shell_path, "sh", "-c", command.c_str(), (char *)NULL);

				// can only reach this point if exec() failed

				// parent can get exit code from waitpid()
				::_exit(errno);
			// using std::exit() would make static dtors run twice

			case -1:
				// couldn't fork, error already handled in pstreambuf::fork()
				break;

			default:
				// this is the parent process
				// activate buffers
				create_buffers(mode);
				ret = this;
			}
		}

		return ret;
#endif
	}

	/**
	 * @brief  Helper function to close a file descriptor.
	 *
	 * Inspects @a fd and calls <b>close</b>(3) if it has a non-negative value.
	 *
	 * @param   fd  a file descriptor.
	 * @relates basic_pstreambuf
	 */
	inline void
	close_fd (pstreams::fd_type &fd) {
		if (fd >= 0 && ::close(fd) == 0) {
			fd = -1;
		}
	}

	/**
	 * @brief  Helper function to close an array of file descriptors.
	 *
	 * Calls @c close_fd() on each member of the array.
	 * The length of the array is determined automatically by
	 * template argument deduction to avoid errors.
	 *
	 * @param   fds  an array of file descriptors.
	 * @relates basic_pstreambuf
	 */
	template<int N>
	inline void
	close_fd_array (pstreams::fd_type(&fds)[N]) {
		for (std::size_t i = 0; i < N; ++i) {
			close_fd(fds[i]);
		}
	}

	/**
	 * Starts a new process by executing @a file with the arguments in
	 * @a argv and opens pipes to the process with the specified @a mode.
	 *
	 * By convention @c argv[0] should be the file name of the file being
	 * executed.
	 *
	 * If @a mode contains @c pstdout the initial read source will be
	 * the child process' stdout, otherwise if @a mode  contains @c pstderr
	 * the initial read source will be the child's stderr.
	 *
	 * Will duplicate the actions of  the  shell  in searching for an
	 * executable file if the specified file name does not contain a slash (/)
	 * character.
	 *
	 * Iff @a file is successfully executed then is_open() will return true.
	 * Otherwise, pstreambuf::error() can be used to obtain the value of
	 * @c errno that was set by <b>execvp</b>(3) in the child process.
	 *
	 * The exit status of the new process will be returned by
	 * pstreambuf::status() after pstreambuf::exited() returns true.
	 *
	 * @param   file  a string containing the pathname of a program to execute.
	 * @param   argv  a vector of argument strings passed to the new program.
	 * @param   mode  a bitwise OR of one or more of @c out, @c in and @c err.
	 * @return  NULL if a pipe could not be opened or if the program could
	 *          not be executed, @c this otherwise.
	 * @see     <b>execvp</b>(3)
	 */
	template<typename C, typename T>
	basic_pstreambuf<C, T> *
	basic_pstreambuf<C, T>::open (const std::string &file,
	                              const argv_type &argv,
	                              pmode mode) {
		basic_pstreambuf<C, T> *ret = NULL;

		if (!is_open()) {
			// constants for read/write ends of pipe
			enum {RD, WR};

			// open another pipe and set close-on-exec
			fd_type ck_exec [] = {-1, -1};
			if (-1 == ::pipe(ck_exec)
			    || -1 == ::fcntl(ck_exec[RD], F_SETFD, FD_CLOEXEC)
			    || -1 == ::fcntl(ck_exec[WR], F_SETFD, FD_CLOEXEC)) {
				error_ = errno;
				close_fd_array(ck_exec);
			} else {
				switch (fork(mode)) {
				case 0:
					// this is the new process, exec command
				{
					char **arg_v = new char *[argv.size() + 1];

					for (std::size_t i = 0; i < argv.size(); ++i) {
						const std::string &src = argv[i];
						char * &dest = arg_v[i];
						dest = new char[src.size() + 1];
						dest[src.copy(dest, src.size())] = '\0';
					}

					arg_v[argv.size()] = NULL;

					::execvp(file.c_str(), arg_v);

					// can only reach this point if exec() failed

					// parent can get error code from ck_exec pipe
					error_ = errno;

					while (::write(ck_exec[WR], &error_, sizeof(error_)) == -1
					       && errno == EINTR)
					{}

					::close(ck_exec[WR]);
					::close(ck_exec[RD]);

					::_exit(error_);
					// using std::exit() would make static dtors run twice
				}

				case -1:
					// couldn't fork, error already handled in pstreambuf::fork()
					close_fd_array(ck_exec);
					break;

				default:
					// this is the parent process

					// check child called exec() successfully
					::close(ck_exec[WR]);

					switch (::read(ck_exec[RD], &error_, sizeof(error_))) {
					case 0:
						// activate buffers
						create_buffers(mode);
						ret = this;
						break;
					case -1:
						error_ = errno;
						break;
					default:
						// error_ contains error code from child
						// call wait() to clean up and set ppid_ to 0
						this->wait();
						break;
					}

					::close(ck_exec[RD]);
				}
			}
		}

		return ret;
	}

	/**
	 * Creates pipes as specified by @a mode and calls @c fork() to create
	 * a new process. If the fork is successful the parent process stores
	 * the child's PID and the opened pipes and the child process replaces
	 * its standard streams with the opened pipes.
	 *
	 * If an error occurs the error code will be set to one of the possible
	 * errors for @c pipe() or @c fork().
	 * See your system's documentation for these error codes.
	 *
	 * @param   mode  an OR of pmodes specifying which of the child's
	 *                standard streams to connect to.
	 * @return  On success the PID of the child is returned in the parent's
	 *          context and zero is returned in the child's context.
	 *          On error -1 is returned and the error code is set appropriately.
	 */
	template<typename C, typename T>
	pid_t
	basic_pstreambuf<C, T>::fork (pmode mode) {
		pid_t pid = -1;

		// Three pairs of file descriptors, for pipes connected to the
		// process' stdin, stdout and stderr
		// (stored in a single array so close_fd_array() can close all at once)
		fd_type fd [] = {-1, -1, -1, -1, -1, -1};
		fd_type *const pin = fd;
		fd_type *const pout = fd + 2;
		fd_type *const perr = fd + 4;

		// constants for read/write ends of pipe
		enum {RD, WR};

		// N.B.
		// For the pstreambuf pin is an output stream and
		// pout and perr are input streams.

		if (!error_ && mode & pstdin && ::pipe(pin)) {
			error_ = errno;
		}

		if (!error_ && mode & pstdout && ::pipe(pout)) {
			error_ = errno;
		}

		if (!error_ && mode & pstderr && ::pipe(perr)) {
			error_ = errno;
		}

		if (!error_) {
			pid = ::fork();

			switch (pid) {
			case 0:
			{
				// this is the new process

				// for each open pipe close one end and redirect the
				// respective standard stream to the other end

				if (*pin >= 0) {
					::close(pin[WR]);
					::dup2(pin[RD], STDIN_FILENO);
					::close(pin[RD]);
				}

				if (*pout >= 0) {
					::close(pout[RD]);
					::dup2(pout[WR], STDOUT_FILENO);
					::close(pout[WR]);
				}

				if (*perr >= 0) {
					::close(perr[RD]);
					::dup2(perr[WR], STDERR_FILENO);
					::close(perr[WR]);
				}

#ifdef _POSIX_JOB_CONTROL
				// Change to a new process group
				::setpgid(0, 0);
#endif

				break;
			}
			case -1:
			{
				// couldn't fork for some reason
				error_ = errno;
				// close any open pipes
				close_fd_array(fd);
				break;
			}
			default:
			{
				// this is the parent process, store process' pid
				ppid_ = pid;

				// store one end of open pipes and close other end
				if (*pin >= 0) {
					wpipe_ = pin[WR];
					::close(pin[RD]);
				}

				if (*pout >= 0) {
					rpipe_[rsrc_out] = pout[RD];
					::close(pout[WR]);
				}

				if (*perr >= 0) {
					rpipe_[rsrc_err] = perr[RD];
					::close(perr[WR]);
				}
			}
			}
		} else {
			// close any pipes we opened before failure
			close_fd_array(fd);
		}

		return pid;
	}

	/**
	 * Closes all pipes and calls wait() to wait for the process to finish.
	 * If an error occurs the error code will be set to one of the possible
	 * errors for @c waitpid().
	 * See your system's documentation for these errors.
	 *
	 * @return  @c this on successful close or @c NULL if there is no
	 *          process to close or if an error occurs.
	 */
	template<typename C, typename T>
	basic_pstreambuf<C, T> *
	basic_pstreambuf<C, T>::close () {
		const bool running = is_open();

		sync();	// this might call wait() and reap the child process

		// rather than trying to work out whether or not we need to clean up
		// just do it anyway, all cleanup functions are safe to call twice.

		destroy_buffers(pstdin | pstdout | pstderr);

		// close pipes before wait() so child gets EOF/SIGPIPE
		close_fd(wpipe_);
		close_fd_array(rpipe_);

		do {
			error_ = 0;
		} while (wait() == -1 && error() == EINTR);

		return running ? this : NULL;
	}

	/**
	 *  Called on construction to initialise the arrays used for reading.
	 */
	template<typename C, typename T>
	inline void
	basic_pstreambuf<C, T>::init_rbuffers () {
		rpipe_[rsrc_out] = rpipe_[rsrc_err] = -1;
		rbuffer_[rsrc_out] = rbuffer_[rsrc_err] = NULL;
		rbufstate_[0] = rbufstate_[1] = rbufstate_[2] = NULL;
	}

	template<typename C, typename T>
	void
	basic_pstreambuf<C, T>::create_buffers (pmode mode) {
		if (mode & pstdin) {
			delete [] wbuffer_;
			wbuffer_ = new char_type[bufsz];
			this->setp(wbuffer_, wbuffer_ + bufsz);
		}

		if (mode & pstdout) {
			delete [] rbuffer_[rsrc_out];
			rbuffer_[rsrc_out] = new char_type[bufsz];
			rsrc_ = rsrc_out;
			this->setg(rbuffer_[rsrc_out] + pbsz, rbuffer_[rsrc_out] + pbsz,
			           rbuffer_[rsrc_out] + pbsz);
		}

		if (mode & pstderr) {
			delete [] rbuffer_[rsrc_err];
			rbuffer_[rsrc_err] = new char_type[bufsz];
			if (!(mode & pstdout)) {
				rsrc_ = rsrc_err;
				this->setg(rbuffer_[rsrc_err] + pbsz, rbuffer_[rsrc_err] + pbsz,
				           rbuffer_[rsrc_err] + pbsz);
			}
		}
	}

	template<typename C, typename T>
	void
	basic_pstreambuf<C, T>::destroy_buffers (pmode mode) {
		if (mode & pstdin) {
			this->setp(NULL, NULL);
			delete [] wbuffer_;
			wbuffer_ = NULL;
		}

		if (mode & pstdout) {
			if (rsrc_ == rsrc_out) {
				this->setg(NULL, NULL, NULL);
			}

			delete [] rbuffer_[rsrc_out];
			rbuffer_[rsrc_out] = NULL;
		}

		if (mode & pstderr) {
			if (rsrc_ == rsrc_err) {
				this->setg(NULL, NULL, NULL);
			}

			delete [] rbuffer_[rsrc_err];
			rbuffer_[rsrc_err] = NULL;
		}
	}

	template<typename C, typename T>
	typename basic_pstreambuf<C, T>::buf_read_src
	basic_pstreambuf<C, T>::switch_read_buffer (buf_read_src src) {
		if (rsrc_ != src) {
			char_type *tmpbufstate [] = {this->eback(), this->gptr(), this->egptr()};
			this->setg(rbufstate_[0], rbufstate_[1], rbufstate_[2]);

			for (std::size_t i = 0; i < 3; ++i) {
				rbufstate_[i] = tmpbufstate[i];
			}

			rsrc_ = src;
		}

		return rsrc_;
	}

	/**
	 * Suspends execution and waits for the associated process to exit, or
	 * until a signal is delivered whose action is to terminate the current
	 * process or to call a signal handling function. If the process has
	 * already exited (i.e. it is a "zombie" process) then wait() returns
	 * immediately.  Waiting for the child process causes all its system
	 * resources to be freed.
	 *
	 * error() will return EINTR if wait() is interrupted by a signal.
	 *
	 * @param   nohang  true to return immediately if the process has not exited.
	 * @return  1 if the process has exited and wait() has not yet been called.
	 *          0 if @a nohang is true and the process has not exited yet.
	 *          -1 if no process has been started or if an error occurs,
	 *          in which case the error can be found using error().
	 */
	template<typename C, typename T>
	int
	basic_pstreambuf<C, T>::wait (bool nohang) {
		int exited = -1;

		if (is_open()) {
			int status;

			switch (::waitpid(ppid_, &status, nohang ? WNOHANG : 0)) {
			case 0:
				// nohang was true and process has not exited
				exited = 0;
				break;
			case -1:
				error_ = errno;
				break;
			default:
				// process has exited
				ppid_ = 0;
				status_ = status;
				exited = 1;
				// Close wpipe, would get SIGPIPE if we used it.
				destroy_buffers(pstdin);
				close_fd(wpipe_);
				// Must free read buffers and pipes on destruction
				// or next call to open()/close()
				break;
			}
		}

		return exited;
	}

	/**
	 * Sends the specified signal to the process.  A signal can be used to
	 * terminate a child process that would not exit otherwise.
	 *
	 * If an error occurs the error code will be set to one of the possible
	 * errors for @c kill().  See your system's documentation for these errors.
	 *
	 * @param   signal  A signal to send to the child process.
	 * @return  @c this or @c NULL if @c kill() fails.
	 */
	template<typename C, typename T>
	inline basic_pstreambuf<C, T> *
	basic_pstreambuf<C, T>::kill (int signal) {
		basic_pstreambuf<C, T> *ret = NULL;
		if (is_open()) {
			if (::kill(ppid_, signal)) {
				error_ = errno;
			} else {
#if 0
				// TODO call exited() to check for exit and clean up? leave to user?
				if (signal == SIGTERM || signal == SIGKILL) {
					this->exited();
				}

#endif
				ret = this;
			}
		}

		return ret;
	}

	/**
	 * Sends the specified signal to the process group of the child process.
	 * A signal can be used to terminate a child process that would not exit
	 * otherwise, or to kill the process and its own children.
	 *
	 * If an error occurs the error code will be set to one of the possible
	 * errors for @c getpgid() or @c kill().  See your system's documentation
	 * for these errors. If the child is in the current process group then
	 * NULL will be returned and the error code set to EPERM.
	 *
	 * @param   signal  A signal to send to the child process.
	 * @return  @c this on success or @c NULL on failure.
	 */
	template<typename C, typename T>
	inline basic_pstreambuf<C, T> *
	basic_pstreambuf<C, T>::killpg (int signal) {
		basic_pstreambuf<C, T> *ret = NULL;
#ifdef _POSIX_JOB_CONTROL
		if (is_open()) {
			pid_t pgid = ::getpgid(ppid_);
			if (pgid == -1) {
				error_ = errno;
			} else if (pgid == ::getpgrp()) {
				error_ = EPERM;	// Don't commit suicide
			} else if (::killpg(pgid, signal)) {
				error_ = errno;
			} else {
				ret = this;
			}
		}

#endif
		return ret;
	}

	/**
	 *  This function can call pstreambuf::wait() and so may change the
	 *  object's state if the child process has already exited.
	 *
	 *  @return  True if the associated process has exited, false otherwise.
	 *  @see     basic_pstreambuf<C,T>::wait()
	 */
	template<typename C, typename T>
	inline bool
	basic_pstreambuf<C, T>::exited () {
		return ppid_ == 0 || wait(true) == 1;
	}

	/**
	 *  @return  The exit status of the child process, or -1 if wait()
	 *           has not yet been called to wait for the child to exit.
	 *  @see     basic_pstreambuf<C,T>::wait()
	 */
	template<typename C, typename T>
	inline int
	basic_pstreambuf<C, T>::status () const {
		return status_;
	}

	/**
	 *  @return  The error code of the most recently failed operation, or zero.
	 */
	template<typename C, typename T>
	inline int
	basic_pstreambuf<C, T>::error () const {
		return error_;
	}

	/**
	 *  Closes the output pipe, causing the child process to receive the
	 *  end-of-file indicator on subsequent reads from its @c stdin stream.
	 */
	template<typename C, typename T>
	inline void
	basic_pstreambuf<C, T>::peof () {
		sync();
		destroy_buffers(pstdin);
		close_fd(wpipe_);
	}

	/**
	 * Unlike pstreambuf::exited(), this function will not call wait() and
	 * so will not change the object's state.  This means that once a child
	 * process is executed successfully this function will continue to
	 * return true even after the process exits (until wait() is called.)
	 *
	 * @return  true if a previous call to open() succeeded and wait() has
	 *          not been called and determined that the process has exited,
	 *          false otherwise.
	 */
	template<typename C, typename T>
	inline bool
	basic_pstreambuf<C, T>::is_open () const {
		return ppid_ > 0;
	}

	/**
	 * Toggle the stream used for reading. If @a readerr is @c true then the
	 * process' @c stderr output will be used for subsequent extractions, if
	 * @a readerr is false the the process' stdout will be used.
	 * @param   readerr  @c true to read @c stderr, @c false to read @c stdout.
	 * @return  @c true if the requested stream is open and will be used for
	 *          subsequent extractions, @c false otherwise.
	 */
	template<typename C, typename T>
	inline bool
	basic_pstreambuf<C, T>::read_err (bool readerr) {
		buf_read_src src = readerr ? rsrc_err : rsrc_out;

		if (rpipe_[src] >= 0) {
			switch_read_buffer(src);
			return true;
		}

		return false;
	}

	/**
	 * Called when the internal character buffer is not present or is full,
	 * to transfer the buffer contents to the pipe.
	 *
	 * @param   c  a character to be written to the pipe.
	 * @return  @c traits_type::eof() if an error occurs, otherwise if @a c
	 *          is not equal to @c traits_type::eof() it will be buffered and
	 *          a value other than @c traits_type::eof() returned to indicate
	 *          success.
	 */
	template<typename C, typename T>
	typename basic_pstreambuf<C, T>::int_type
	basic_pstreambuf<C, T>::overflow (int_type c) {
		if (!empty_buffer()) {
			return traits_type::eof();
		} else if (!traits_type::eq_int_type(c, traits_type::eof())) {
			return this->sputc(c);
		} else {
			return traits_type::not_eof(c);
		}
	}

	template<typename C, typename T>
	int
	basic_pstreambuf<C, T>::sync () {
		return !exited() && empty_buffer() ? 0 : -1;
	}

	/**
	 * @param   s  character buffer.
	 * @param   n  buffer length.
	 * @return  the number of characters written.
	 */
	template<typename C, typename T>
	std::streamsize
	basic_pstreambuf<C, T>::xsputn (const char_type *s, std::streamsize n) {
		std::streamsize done = 0;

		while (done < n) {
			if (std::streamsize nbuf = this->epptr() - this->pptr()) {
				nbuf = std::min(nbuf, n - done);
				traits_type::copy(this->pptr(), s + done, nbuf);
				this->pbump(nbuf);
				done += nbuf;
			} else if (!empty_buffer()) {
				break;
			}
		}

		return done;
	}

	/**
	 * @return  true if the buffer was emptied, false otherwise.
	 */
	template<typename C, typename T>
	bool
	basic_pstreambuf<C, T>::empty_buffer () {
		const std::streamsize count = this->pptr() - this->pbase();

		if (count > 0) {
			const std::streamsize written = this->write(this->wbuffer_, count);
			if (written > 0) {
				if (const std::streamsize unwritten = count - written) {
					traits_type::move(this->pbase(), this->pbase() + written, unwritten);
				}

				this->pbump(-written);
				return true;
			}
		}

		return false;
	}

	/**
	 * Called when the internal character buffer is is empty, to re-fill it
	 * from the pipe.
	 *
	 * @return The first available character in the buffer,
	 * or @c traits_type::eof() in case of failure.
	 */
	template<typename C, typename T>
	typename basic_pstreambuf<C, T>::int_type
	basic_pstreambuf<C, T>::underflow () {
		if (this->gptr() < this->egptr() || fill_buffer()) {
			return traits_type::to_int_type(*this->gptr());
		} else {
			return traits_type::eof();
		}
	}

	/**
	 * Attempts to make @a c available as the next character to be read by
	 * @c sgetc().
	 *
	 * @param   c   a character to make available for extraction.
	 * @return  @a c if the character can be made available,
	 *          @c traits_type::eof() otherwise.
	 */
	template<typename C, typename T>
	typename basic_pstreambuf<C, T>::int_type
	basic_pstreambuf<C, T>::pbackfail (int_type c) {
		if (this->gptr() != this->eback()) {
			this->gbump(-1);
			if (!traits_type::eq_int_type(c, traits_type::eof())) {
				*this->gptr() = traits_type::to_char_type(c);
			}

			return traits_type::not_eof(c);
		} else {
			return traits_type::eof();
		}
	}

	template<typename C, typename T>
	std::streamsize
	basic_pstreambuf<C, T>::showmanyc () {
		int avail = 0;

		if (sizeof(char_type) == 1) {
			avail = fill_buffer(true) ? this->egptr() - this->gptr() : -1;
		}

#ifdef FIONREAD
		else {
			if (::ioctl(rpipe(), FIONREAD, &avail) == -1) {
				avail = -1;
			} else if (avail) {
				avail /= sizeof(char_type);
			}
		}
#endif
		return std::streamsize(avail);
	}

	/**
	 * @return  true if the buffer was filled, false otherwise.
	 */
	template<typename C, typename T>
	bool
	basic_pstreambuf<C, T>::fill_buffer (bool non_blocking) {
		const std::streamsize pb1 = this->gptr() - this->eback();
		const std::streamsize pb2 = pbsz;
		const std::streamsize npb = std::min(pb1, pb2);
		char_type *const rbuf = rbuffer();

		traits_type::move(rbuf + pbsz - npb, this->gptr() - npb, npb);

		std::streamsize rc = -1;

		if (non_blocking) {
			const int flags = ::fcntl(rpipe(), F_GETFL);
			if (flags != -1) {
				const bool blocking = !(flags & O_NONBLOCK);
				if (blocking) {
					::fcntl(rpipe(), F_SETFL, flags | O_NONBLOCK);	// set non-blocking
				}

				error_ = 0;
				rc = read(rbuf + pbsz, bufsz - pbsz);

				if (rc == -1 && error_ == EAGAIN) {	// nothing available
					rc = 0;
				} else if (rc == 0) {	// EOF
					rc = -1;
				}

				if (blocking) {
					::fcntl(rpipe(), F_SETFL, flags);	// restore
				}
			}
		} else {
			rc = read(rbuf + pbsz, bufsz - pbsz);
		}

		if (rc > 0 || (rc == 0 && non_blocking)) {
			this->setg(rbuf + pbsz - npb,
			           rbuf + pbsz,
			           rbuf + pbsz + rc);
			return true;
		} else {
			this->setg(NULL, NULL, NULL);
			return false;
		}
	}

	/**
	 * Writes up to @a n characters to the pipe from the buffer @a s.
	 *
	 * @param   s  character buffer.
	 * @param   n  buffer length.
	 * @return  the number of characters written.
	 */
	template<typename C, typename T>
	inline std::streamsize
	basic_pstreambuf<C, T>::write (const char_type *s, std::streamsize n) {
		std::streamsize nwritten = 0;

		if (wpipe() >= 0) {
			nwritten = ::write(wpipe(), s, n * sizeof(char_type));
			if (nwritten == -1) {
				error_ = errno;
			} else {
				nwritten /= sizeof(char_type);
			}
		}

		return nwritten;
	}

	/**
	 * Reads up to @a n characters from the pipe to the buffer @a s.
	 *
	 * @param   s  character buffer.
	 * @param   n  buffer length.
	 * @return  the number of characters read.
	 */
	template<typename C, typename T>
	inline std::streamsize
	basic_pstreambuf<C, T>::read (char_type *s, std::streamsize n) {
		std::streamsize nread = 0;

		if (rpipe() >= 0) {
			nread = ::read(rpipe(), s, n * sizeof(char_type));
			if (nread == -1) {
				error_ = errno;
			} else {
				nread /= sizeof(char_type);
			}
		}

		return nread;
	}

	/** @return a reference to the output file descriptor */
	template<typename C, typename T>
	inline pstreams::fd_type &
	basic_pstreambuf<C, T>::wpipe () {
		return wpipe_;
	}

	/** @return a reference to the active input file descriptor */
	template<typename C, typename T>
	inline pstreams::fd_type &
	basic_pstreambuf<C, T>::rpipe () {
		return rpipe_[rsrc_];
	}

	/** @return a reference to the specified input file descriptor */
	template<typename C, typename T>
	inline pstreams::fd_type &
	basic_pstreambuf<C, T>::rpipe (buf_read_src which) {
		return rpipe_[which];
	}

	/** @return a pointer to the start of the active input buffer area. */
	template<typename C, typename T>
	inline typename basic_pstreambuf<C, T>::char_type *
	basic_pstreambuf<C, T>::rbuffer () {
		return rbuffer_[rsrc_];
	}

	/*
	 * member definitions for pstream_common
	 */

	/**
	 * @class pstream_common
	 * Abstract Base Class providing common functionality for basic_ipstream,
	 * basic_opstream and basic_pstream.
	 * pstream_common manages the basic_pstreambuf stream buffer that is used
	 * by the derived classes to initialise an iostream class.
	 */

	/** Creates an uninitialised stream. */
	template<typename C, typename T>
	inline
	pstream_common<C, T>::pstream_common ()
		: std::basic_ios<C, T>(NULL)
		, command_()
		, buf_() {
		this->std::basic_ios<C, T>::rdbuf(&buf_);
	}

	/**
	 * Initialises the stream buffer by calling
	 * do_open( @a command , @a mode )
	 *
	 * @param command a string containing a shell command.
	 * @param mode    the I/O mode to use when opening the pipe.
	 * @see   do_open(const std::string&, pmode)
	 */
	template<typename C, typename T>
	inline
	pstream_common<C, T>::pstream_common (const std::string &command, pmode mode)
		: std::basic_ios<C, T>(NULL)
		, command_(command)
		, buf_() {
		this->std::basic_ios<C, T>::rdbuf(&buf_);
		do_open(command, mode);
	}

	/**
	 * Initialises the stream buffer by calling
	 * do_open( @a file , @a argv , @a mode )
	 *
	 * @param file  a string containing the pathname of a program to execute.
	 * @param argv  a vector of argument strings passed to the new program.
	 * @param mode  the I/O mode to use when opening the pipe.
	 * @see do_open(const std::string&, const argv_type&, pmode)
	 */
	template<typename C, typename T>
	inline
	pstream_common<C, T>::pstream_common (const std::string &file,
	                                      const argv_type &argv,
	                                      pmode mode)
		: std::basic_ios<C, T>(NULL)
		, command_(file)
		, buf_() {
		this->std::basic_ios<C, T>::rdbuf(&buf_);
		do_open(file, argv, mode);
	}

	/**
	 * This is a pure virtual function to make @c pstream_common abstract.
	 * Because it is the destructor it will be called by derived classes
	 * and so must be defined.  It is also protected, to discourage use of
	 * the PStreams classes through pointers or references to the base class.
	 *
	 * @sa If defining a pure virtual seems odd you should read
	 * http://www.gotw.ca/gotw/031.htm (and the rest of the site as well!)
	 */
	template<typename C, typename T>
	inline
	pstream_common<C, T>::~pstream_common ()
	{}

	/**
	 * Calls rdbuf()->open( @a command , @a mode )
	 * and sets @c failbit on error.
	 *
	 * @param command a string containing a shell command.
	 * @param mode    the I/O mode to use when opening the pipe.
	 * @see   basic_pstreambuf::open(const std::string&, pmode)
	 */
	template<typename C, typename T>
	inline void
	pstream_common<C, T>::do_open (const std::string &command, pmode mode) {
		if (!buf_.open((command_ = command), mode)) {
			this->setstate(std::ios_base::failbit);
		}
	}

	/**
	 * Calls rdbuf()->open( @a file, @a  argv, @a mode )
	 * and sets @c failbit on error.
	 *
	 * @param file  a string containing the pathname of a program to execute.
	 * @param argv  a vector of argument strings passed to the new program.
	 * @param mode  the I/O mode to use when opening the pipe.
	 * @see   basic_pstreambuf::open(const std::string&, const argv_type&, pmode)
	 */
	template<typename C, typename T>
	inline void
	pstream_common<C, T>::do_open (const std::string &file,
	                               const argv_type &argv,
	                               pmode mode) {
		if (!buf_.open((command_ = file), argv, mode)) {
			this->setstate(std::ios_base::failbit);
		}
	}

	/** Calls rdbuf->close() and sets @c failbit on error. */
	template<typename C, typename T>
	inline void
	pstream_common<C, T>::close () {
		if (!buf_.close()) {
			this->setstate(std::ios_base::failbit);
		}
	}

	/**
	 * @return  rdbuf()->is_open().
	 * @see     basic_pstreambuf::is_open()
	 */
	template<typename C, typename T>
	inline bool
	pstream_common<C, T>::is_open () const {
		return buf_.is_open();
	}

	/** @return a string containing the command used to initialise the stream. */
	template<typename C, typename T>
	inline const std::string &
	pstream_common<C, T>::command () const {
		return command_;
	}

	/** @return a pointer to the private stream buffer member. */
	// TODO  document behaviour if buffer replaced.
	template<typename C, typename T>
	inline typename pstream_common<C, T>::streambuf_type *
	pstream_common<C, T>::rdbuf () const {
		return const_cast<streambuf_type *>(&buf_);
	}

#if REDI_EVISCERATE_PSTREAMS
	/**
	 * @def REDI_EVISCERATE_PSTREAMS
	 * If this macro has a non-zero value then certain internals of the
	 * @c basic_pstreambuf template class are exposed. In general this is
	 * a Bad Thing, as the internal implementation is largely undocumented
	 * and may be subject to change at any time, so this feature is only
	 * provided because it might make PStreams useful in situations where
	 * it is necessary to do Bad Things.
	 */

	/**
	 * @warning  This function exposes the internals of the stream buffer and
	 *           should be used with caution. It is the caller's responsibility
	 *           to flush streams etc. in order to clear any buffered data.
	 *           The POSIX.1 function <b>fdopen</b>(3) is used to obtain the
	 *           @c FILE pointers from the streambuf's private file descriptor
	 *           members so consult your system's documentation for
	 *           <b>fdopen</b>(3).
	 *
	 * @param   in    A FILE* that will refer to the process' stdin.
	 * @param   out   A FILE* that will refer to the process' stdout.
	 * @param   err   A FILE* that will refer to the process' stderr.
	 * @return  An OR of zero or more of @c pstdin, @c pstdout, @c pstderr.
	 *
	 * For each open stream shared with the child process a @c FILE* is
	 * obtained and assigned to the corresponding parameter. For closed
	 * streams @c NULL is assigned to the parameter.
	 * The return value can be tested to see which parameters should be
	 * @c !NULL by masking with the corresponding @c pmode value.
	 *
	 * @see <b>fdopen</b>(3)
	 */
	template<typename C, typename T>
	std::size_t
	basic_pstreambuf<C, T>::fopen (FILE * &in, FILE * &out, FILE * &err) {
		in = out = err = NULL;
		std::size_t open_files = 0;
		if (wpipe() > -1) {
			if ((in = ::fdopen(wpipe(), "w"))) {
				open_files |= pstdin;
			}
		}

		if (rpipe(rsrc_out) > -1) {
			if ((out = ::fdopen(rpipe(rsrc_out), "r"))) {
				open_files |= pstdout;
			}
		}

		if (rpipe(rsrc_err) > -1) {
			if ((err = ::fdopen(rpipe(rsrc_err), "r"))) {
				open_files |= pstderr;
			}
		}

		return open_files;
	}

	/**
	 *  @warning This function exposes the internals of the stream buffer and
	 *  should be used with caution.
	 *
	 *  @param  in   A FILE* that will refer to the process' stdin.
	 *  @param  out  A FILE* that will refer to the process' stdout.
	 *  @param  err  A FILE* that will refer to the process' stderr.
	 *  @return A bitwise-or of zero or more of @c pstdin, @c pstdout, @c pstderr.
	 *  @see    basic_pstreambuf::fopen()
	 */
	template<typename C, typename T>
	inline std::size_t
	pstream_common<C, T>::fopen (FILE * &fin, FILE * &fout, FILE * &ferr) {
		return buf_.fopen(fin, fout, ferr);
	}

#endif	// REDI_EVISCERATE_PSTREAMS
}	// namespace redi

/**
 * @mainpage PStreams Reference
 * @htmlinclude mainpage.html
 */

#endif	// REDI_PSTREAM_H_SEEN

// vim: ts=2 sw=2 expandtab

